1. Technical Field
This invention relates to telecommunications exchange or router installations and to methods of creating connections and re-routing connections in such installations.
2. Related Art
A typical telecommunications exchange building houses a large variety and quantity of equipment such as switches, typically on equipment racks, and connected by cables to and from each other and to the external telecommunications network. The trunk parts of telecommunications networks are nowadays commonly all-fibre. Increasingly, optical fibre use extends into the access network, with fibre-to-the kerb, fibre-to-the-cabinet and even fibre-to-the premises. Consequently, virtually all modern telephone exchange installations involve a considerable proportion of fibre circuits rather than wired circuits. Because optical fibre is sensitive both to bend and strain, management of the optical interconnections within an exchange installation is important.
One of the main functions of optical fibre plant within an exchange or router building is to manage and route fibres from a particular set of optical equipment to fibres from, for example, an incoming cable from the external telecommunications network. As optical fibre is deployed more abundantly and more generally in the network, the routing and patching of such fibre, especially within exchanges, is becoming increasingly troublesome. Major problems are the growth in the amount of equipment and the sheer number of connections required. These problems are exacerbated by growth, upgrading and changes within the exchange which result in the need to interconnect new equipment or systems. Although the physical positions of incoming cables rarely change, additional cables may be added and the new equipment or system will almost certainly be in a different physical location from the old, and in any event will typically need moving or different connections to be made.
The current method of fibre routing within exchange buildings is achieved with Optical Flexibility Racks (OFRs), which serve as junction or distribution points allowing cables to be routed within the exchange building. OFRs can carry hundreds of individually spliced fibres but when they are fully populated, as is often the case, there is severe congestion at the OFRs. It is often difficult to identify, locate and isolate individual fibres in such cases when re-routing of the cable path is necessary, making the task both time-consuming and complicated. Another problem resulting from fibre overcrowding is that fibres are routed across each other in close proximity so that the combined weight presses down on fibres located near the base of OFRs, increasing the risk of circuit failure through increased optical loss and even of fibre breakage. This problem becomes even more critical as higher bit rate systems are employed, as these tend to be more sensitive to increases in optical loss.
The installation and maintenance of optical fibre cabling, its routing and supporting structures such as OFRs take up a significant portion of the total cost, time and effort of installing and cabling a telecommunications exchange system. The current methods to interconnect exchange equipment, or to connect an incoming cable to a rack of exchange equipment typically involve several lengths of optical fibre connected end to end either by means of connectors or splices, or a combination thereof. The path taken by the fibre from the incoming cable to an equipment rack could involve a significant number of connections or splices, especially if the destination equipment rack is physically distant from the incoming cable, for example if the equipment sits on a separate floor from the incoming cable within the exchange building.
Such conventional methods are commonly known and described in e.g. Modular Optical Plant for Access Network, Operational Aspects by D. Brewer et. al (Proc. EFOC & N (Technology and Infrastructure) 1995, at pages 164-167).
Problems associated with the existing method of creating fibre paths by using connectors or splices arise from the inherently delicate nature of joining fibre ends, which is time- and cost-consuming in the need for specialist equipment and expertise. Connections and splicing also inevitably involve optical losses regardless of the quality of the joint. Other problems could arise: for example, stored fibre could “run out” either side of the splice, thereby reducing the number of fibre turns and hence the opportunity to re-splice in the future.